Hey friend! Have fun exploring Q&A, but in order to ask your own
questions, comment, or give thumbs up, you need to be logged in to your
Moz Pro account.
You can also earn access by receiving 500
MozPoints
from participating in YouMoz and the Moz Blog!

Just to be on the safe side, I'd also check to see if there were any changes made to pages between December and January -- is there a section of the site that has GA code installed twice and you're getting no bounce rate for part of the site? Or some other element or GA configuration that is causing something else to load? That drop is fairly dramatic between December and January.

I discovered I had a custom GA script on my site and had left the Wordpress GA plugin active, so I had GA twice on my site and had about a 1% bounce rate. 12.35% is an awesome low bounce rate, but I'd poke around a little bit in my analytics and see if I can find particular pages or sections with a less than 1% bounce rate that might indicate an installation or code issue.

Hey friend! Have fun exploring Q&A, but in order to ask your own
questions, comment, or give thumbs up, you need to be logged in to your
Moz Pro account.
You can also earn access by receiving 500
MozPoints
from participating in YouMoz and the Moz Blog!
Learn more.